| Optimal FM Ltd | Hillington | A rating |
| Optimal Health Chiropractic | Edinburgh | A rating |
| Optimal Industrial Automation Limited | Yate | A rating |
| Optimal Living (Kent) Ltd | Sittingbourne | A rating |
| Optimal Living (Luton) Ltd | Luton | A rating |
| Optimal Living Ltd. | Swindon | A rating |
| Optimal Maintenance Ltd | London | A rating |
| Optimal Marketing Limited | Bolton | A rating |
| Optimal Pharma Ltd | Dunstable | A rating |
| Optimal Physio Limited | Glasgow | A rating |
| OPTIMAL SPINE & SPORTDIMENSIONS CHISWICK LIMITED | London | A rating |
| Optimal Technologies Limited | Letchworth Garden City | A rating |
| Optimal Vision Limited | London | A rating |
| OPTIMAL WESTMIDLANDS LTD | Birmingham | A rating |
| OptimallyMe Limited | London | A rating |
| OPTIMAPHARM (UK) LIMITED | Oxford | A rating |
| Optimas OE Solutions | GLOUCESTER | A rating |
| Optimatics LLC | Wood Green | A rating |
| Optimax Imaging Inspection and Measurement Limited | Market Harborough | A rating |
| Optimhouse Limited | COVENTRY | A rating |
| Optimised Care Limited T/A Optimised Care | Bromsgrove | A rating |
| Optimised Group Limited | Blackpool | A rating |
| Optimised Training Centre | Birmingham | A rating |
| Optimism Supported Housing | Croydon | A rating |
| OPTIMISTIC TECH SERVICES LIMITED | Manchester | A rating |
| Optimity Ltd | Chippenham | A rating |
| OPTIMIZE LENS UK LIMITED | Leicester | A rating |
| Optimizely Ltd | London | A rating |
| Optiml London UK Limited | London | A rating |
| Optimman Ltd | GLENAVY CRUMLIN | A rating |
| Optimove UK LTD | London | A rating |
| Optimum Care (South) Ltd | Peterborough | A rating |
| OPTIMUM CARE GL LIMITED | BARKING | A rating |
| Optimum Contractors Ltd | Stansted | A rating |
| Optimum Drywall Systems Limited | BRISTOL | A rating |
| Optimum Healthcare Limited | Sheffield | A rating |
| OPTIMUM MEDICAL SOLUTIONS LTD | Leeds | A rating |
| OPTIMUM PALLET SERVICES LIMITED | Ruislip | A rating |
| Optimum SME Finance Ltd | Bristol | A rating |
| Optimum Strategic Communications Limited | London | A rating |
| Optimum Vehicle Management Ltd | Southampton | A rating |
| Optimum Youth Care Limited | Harrow | A rating |
| OPTIMUMCARE 4U LIMITED | Crawley | A rating |
| OPTIMUS BIZ SOLUTIONS LIMITED | Hounslow | A rating |
| Optimus Eight Ltd t/a SMATCHA | London | A rating |
| Optimus Indigo Limited t/a Bubble Magik | London | A rating |
| Optimus IT Infra Ltd | Chiswick | A rating |
| OPTIMUS LONDON PROPERTY MANAGEMENT LTD | London | A rating |
| Optimus Search | LONDON | A rating |
| OPTIMUS TECHNOCRATS | Bury St. Edmunds | A rating |
| OPTIMUS TRADING SERVICES LTD | Swansea | A rating |
| Optimus Yellow Ltd t/a Bubble Magik | London | A rating |
| Optimyzd Ltd | Peterborough | A rating |
| Optinetz Limited | Bletchley | A rating |
| Optio Group Services Limited | London | A rating |
| Optiom Health Ltd | Hitchin | A rating |
| Option Care Ltd | Gloucester | A rating |
| OPTION FASHION UK LTD | LONDON | UK Expansion Worker: Provisional |
| Optionone Services UK Ltd | Dartford | A rating |
| Options Care Limited | Thornton Heath | A rating |
| Options Direct Ltd | richmond | A rating |
| OPTIONS FOR SUPPORTED LIVING | Liverpool | A rating |
| OPTIONS GROUP (UK) LTD | LONDON | A rating |
| Options Group Services UK Limited | MILTON KEYNES | A rating |
| Options health care services Limited | Stevenage | A rating |
| Options Management Ltd | Newcastle -under- Lyme | A rating |
| Options Technology Limited | London | A rating |
| Optiplus Services Limited | Slough | A rating |
| OPTIQUE VISION (DERBY) LIMITED | Derby | A rating |
| OPTIRISK SYSTEMS LTD | UXBRIDGE | A rating |
| Optisolutions Limited | RAINHAM | A rating |
| Optiva Solutions (UK) Limited | Reading | A rating |
| Optiver UK Limited | London | A rating |
| OPTIVEST INVESTMENT LTD | London | A rating |
| Optivet Referrals Ltd | Havant | A rating |
| Optix Software Ltd | York | A rating |
| Optometric Technology Group Ltd | London | A rating |
| Optometrix Ltd t/a Opticalise Opticians | Harrow | A rating |
| Optos Plc | Dunfermline | A rating |
| Optrak Distribution Software Limited | Ware | A rating |
| Optro UK Ltd | London | A rating |
| Optum Health Solutions (UK) Limited | Buckinghamshire | A rating |
| Optum Venture Global Management UK Limited | London | A rating |
| Opulence Engineering Ltd | London | A rating |
| OPULENT EATERY LTD | Banstead | A rating |
| Opulent IT Solutions Ltd | Harrow | A rating |
| Opulent UK 3 Ltd | London | A rating |
| Opulenze Capital Limited | London | A rating |
| Opus 11 Events Limited | London | A rating |
| Opus 2 International Limited | London | A rating |
| OPUS ACCOUNTANCY LIMITED | Knutsford | A rating |
| OPUS ACCOUNTANCY LIMITED | Chester | A rating |
| OPUS Community Limited | London | A rating |
| Opus Corporate Finance LLP | London | A rating |
| Opus Dei Charitable Trust | London | A rating |
| Opus International Products Limited | Leamington Spa | A rating |
| Opus Magnum Ltd | London | A rating |
| Opus Payment Solutions UK Ltd | Milton Keynes | A rating |
| Opus Power Networks Ltd | Limavady | A rating |
| Opus Restructuring LLP | Milton Keynes | A rating |
| Opus Safety Ltd | Birmingham | A rating |
| Opus Talent Solutions Limited | London | A rating |
| Opus Utility Solutions Limited t/a Reddish Plant Services Limited | Culcheth | A rating |
| Opus Waterproofing Solutions Ltd | Borough Green | A rating |
| OpusApeiro Ltd | Bristol | A rating |
| OPUSHAVEN GROUP LTD | Ashford | A rating |
| OPUZ INVESTMENTS AND DEVELOPMENT LTD | Aylesbury | A rating |
| OPUZ LTD | Didcot | A rating |
| Opvia Ltd | London | A rating |
| OQ Trading (UK) Services Limited | London | A rating |
| OQAS Limited | Stockport | A rating |
| OQEMA LIMITED | Carterton | A rating |
| OQX Group Ltd | London | A rating |
| OR Media Limited | London | A rating |
| Or Skye | Portree | A rating |
| OR3D Ltd | Wrexham | A rating |
| Ora Europe Ltd | London | A rating |
| ORACARE (SCOTLAND) LIMITED | Aberdeen | A rating |
| ORACLE CONSTRUCTION PROJECTS LTD | Bolton | A rating |
| Oracle Corporation UK Limited | Reading | A rating |
| Oracle Dental Group | Colchester | A rating |
| Oracle Financial Services Software B.V. | London | A rating |
| ORACLE FOOD BELFAST LTD | Belfast | A rating |
| Oracle Solicitors and Consultants Ltd (Trading as Oracle Law Global) | London | A rating |
| OracleBio Ltd | Motherwell | A rating |
| ORAL CREATIONS DENTAL LABORATORY LTD | Weybridge | A rating |
| ORAL HEALTHCARE WALDRON LTD | London | A rating |
| Oral Vision Ltd | London | A rating |
| Orama Solutions Ltd | London | A rating |
| Oran Homecare Ltd. | Kirkcaldy | A rating |
| Orana Corporate LLP | London | A rating |
| Orange Brand Services Limited | London | A rating |
| Orange Business Holdings UK Limited | Slough | A rating |
| Orange Care - Grange Lea Limited | Paignton | A rating |
| Orange Care Ltd t/a The Beeches Nursing Home | Hayle | A rating |
| Orange Connex Global UK Limited | London | A rating |
| ORANGE COUNTY REAL ESTATE UK LIMITED | London | A rating |
| Orange Court Limited | Chichester | A rating |
| Orange Cyberdefense UK Limited | Maidstone | A rating |
| Orange Hut Limited | Hull | A rating |
| ORANGE ICE CREAM AND DESSERT PARLOUR LTD | Norwich | A rating |
| ORANGE MEDIA LIMITED | London | A rating |
| ORANGE OYS LTD | London | A rating |
| Orange Packaging Limited | London | A rating |
| ORANGE PRIVATE LIMITED | Reading | A rating |
| Orange Shop Ltd T/A Orange Shop Supermarket | Borehamwood | A rating |
| Orange Tree Theatre Ltd | London | A rating |
| Orange Tree Trust | London | A rating |
| ORANGE TWIST LTD | London | A rating |
| Orangebox Supermarkets Limited | England | A rating |
| Oranmac Limited | Newry | A rating |
| Oranmore Precast Ltd | Brandon | A rating |
| Orano Limited | Abingdon | A rating |
| Oraserv Ltd | Solihull | A rating |
| ORB Innovations Ltd | London | A rating |
| ORB International Ltd | Holborn | A rating |
| Orbach & Chambers Ltd | London | A rating |
| Orben Limited | Greater Manchester | A rating |
| Orbian Management Limited | London | A rating |
| Orbin Kitchen Ltd | Uxbridge | A rating |
| Orbis Advisory Limited | London | A rating |
| Orbis Care Limited | Henley in Arden | A rating |
| Orbis Charitable Trust | London | A rating |
| Orbis Consultants Limited | London | A rating |
| Orbis Education and Care | Cardiff | A rating |
| Orbis Investment Advisory Limited | London | A rating |
| Orbis Investments (U.K.) Limited | London | A rating |
| Orbis Partners Limited | Birmingham | A rating |
| Orbis Portfolio Management (Europe) LLP | London | A rating |
| Orbis Support Ltd | North Shields | A rating |
| Orbit Cargo Services Ltd | COLNBROOK | A rating |
| Orbit Discovery Ltd | Oxford | A rating |
| Orbit Fab Ltd | Didcot | A rating |
| Orbit Financial Technology Limited | London | A rating |
| ORBIT FOOD AND BEVERAGE LTD | Croydon | A rating |
| Orbit Food Ltd | Wolverhampton | A rating |
| Orbit Grill Limited | Acton | A rating |
| Orbit iTech Ltd | Birmingham | A rating |
| Orbit Media Solutions Limited | London | A rating |
| Orbit Metro Limited | London | A rating |
| Orbit Partners Limited | London | A rating |
| Orbital Astronautics Ltd | Goring | A rating |
| ORBITAL CARE SERVICES 2 LTD | Kenley | A rating |
| Orbital Civil Engineering Ltd | Essex | A rating |
| Orbital Education Limited | Cheadle Hulme | A rating |
| Orbital Gas Systems Limited | Stone | A rating |
| Orbital Materials Ltd | Elsted | A rating |
| Orbital Mobile Ltd | London | A rating |
| Orbital Net Ltd | Canterbury | A rating |
| Orbital Witness Limited | London | A rating |
| ORBITER AVIATION LIMITED | London | A rating |
| Orbitvu Sales Ltd | Northfield Daventry | A rating |
| Orbix UK limited | Walton-On-Thames | A rating |
| ORBIZ LTD | MANCHESTER | A rating |
| Orbyt Group | London | A rating |
| ORCA BUSINESS SOLUTIONS LTD | HEMEL HEMPSTEAD | A rating |
| ORCA Computing LTD | London | A rating |
| Orca CT Trading Ltd | Corby | A rating |
| Orca Scan Limited | Cambridge | A rating |
| Orca Security UK Ltd | Cambridge | A rating |